This invention relates generally to electrode boiler steam humidifier systems and more particularly to a humidifier controller wherein a corrective cycle is automatically initated when boiler electrode current exceeds a predetermined limit.
The electrode current drawn by the boiler of an electronic steam humidifier system is influenced by a number of factors, including, the quantity and conductivity of the water contained in the boiler, and the degree to which precipitate deposits have accumulated within the boiler. Because these factors are continually changing, boiler electrode current typically varies as the humidifier system operates. Since the instantaneous boiler electrode current can be indicative of the general condition of both the boiler and of the water contained therein, various humidifier controllers have been developed wherein system operation is controlled in response to the instantaneous electrode current drawn by the boiler.
In one prior humidifier controller, which is described in U.S. Pat. No. 4,262,191, issued Apr. 14, 1981 to Lepper et al., additional water is admitted into the boiler when the boiler electrode current drops below a predetermined minimum normal current level. As the water level within the boiler rises, the electrode current increases. When the current rises to a predetermined maximum normal current level, the admission of additional water into the boiler is terminated. As the water is converted to steam, the electrode current drops until the predetermined minimum normal current level is once again reached whereupon the cycle begins anew. System operation is thus such that a substantially constant average electrode current is maintained as the boiler is operated over a period of time.
Although the normal variations in boiler electrode current ordinarily occur gradually and steadily as the boiler is operated, the propensity for accumulated precipitates to suddenly dislodge from the boiler electrodes gives rise to random sudden increases in boiler electrode current. To prevent sustained operation at current levels well in excess of the maximum normal current level, the controller described in the aforesaid patent to Lepper et al. functions to automatically take corrective action by draining a portion of the boiler water over a time period of fixed duration, whenever the boiler electrode current exceeds a predetermined upper limit. By repeatedly draining a portion of the boiler water in this manner, the electrode current can usually be reduced to within the normal operating limits. However, because electrode current in excess of the predetermined upper limit can result from a variety of conditions which are uncorrectable merely through drainage of some of the water from the boiler, it is possible for the controller to enter a never-ending cycle of repeated attempts to drain still more water from the boiler.
In view of the foregoing, it is a general object of the present invention to provide a new and improved humidifier controller for controlling operation of an electrode boiler in accordance with the electrode current drawn thereby.
It is another object of the present invention to provide a humidifier controller wherein corrective action is taken when electrode current exceeds a predetermined upper current limit, but wherein repetitive futile attempts to reduce the electrode current are avoided in the event a predetermined number of such attempts prove ineffective in reducing the electrode current.